Ontario Premier Kathleen Wynne promised Sunday to do everything she can to defeat Stephen Harper and elect Justin Trudeau in the Oct. 19 federal election.

"We need a new Prime Minister," she told The Globe and Mail Sunday. "There's no secret that I'll be working for Justin."

Relations between the Ontario Liberals and the federal Conservatives are toxic on a whole host of issues. The biggest bane may be the refusal by the Harper government to assist in the creation of an Ontario supplement to the Canada Pension Plan.

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Without the support of the Canada Revenue Agency, which Finance Minister Joe Oliver refused to provide because he considers the new pension unaffordable, the Ontario Retirement Pension Plan will be much more expensive to set up and administer, a situation Ms. Wynne said displayed "a blatant lack of respect for the people of Ontario."

Conversely, the ties between the Ontario and federal Liberals verge on intimate. Mr. Trudeau's two most senior advisors, Gerry Butts and Katie Telford, worked in the government of Ms. Wynne's predecessor, Dalton McGuinty. In recent years, the two parties have co-operated in developing a data base that identifies potential Liberal supporters.

Provincial party members will work with their federal counterparts on door-knocking and the like throughout the campaign. And Ms. Wynne will appear with Mr. Trudeau at a number of public events.

Beyond that, the two leaders share a similar vision of the federation: one in which Ottawa works co-operatively with the provinces on national programs. Mr. Harper has preferred to keep the federal government within its own jurisdiction, and to let the provinces do their own thing.

The blessing of the provincial Liberals' support may, however, be mixed. Ms. Wynne's decision to sell off Hydro One has not gone down well, and many immigrant and rural voters are unhappy with the new provincial sex-education curriculum.

But given the strength of the Conservative machine in the province, the federal Liberals will doubtless welcome the help from their provincial cousins.

After all, the same voters who cast ballots for Stephen Harper in 2011 voted for Ms. Wynne in 2014. The Premier could be an especially valuable asset in places such as downtown Toronto, where the fights are between the Liberals and the NDP.

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If Ms. Wynne can help Mr. Trudeau win the election by winning Ontario, then the ties between Queen's Park and Parliament Hill may become the closest Ontario voters have ever seen.

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